A study of the moire topography - An accurate theory and the applicable limit of the divergent light ray method

A new accurate theory for the divergent-light-ray (DLR) method which facilitates the accurate measurement of the surface contour of a three-dimensional concave-convex object - is proposed. It is shown that this new theory provides the same degree of accuracy in the DLR method as that in the collimated-light-ray method without the experimental constraint of taking the distance between camera and measuring object as large as possible to approximate collimated light. A procedure for evaluating the applicable limit of the DLR method is outlined, and the measurement accuracy according to the new theory is examined.